Hi Everyone,

I have a new "challenge". I just recently bought an '86 XJ-12 VDP TWR. I drove it home and everything was fine. It did have a high idle and the PO said that he had been told the AAV needed to be replaced. The idle was somewhere around 13-1400 RPM. After getting it home, I poked around under the hood and noted some vacuum leaks. Nothing serious, and I reconnected them. One was to EAC5086 on the fuel rail, and the other was o the top of the dizzy cap. I also noted that the AAV valve adjustment had been completely screwed in! After making adjustment to the AAV, I went to start it and got a plume of smoke, then she died. I disconnected the main relay, and she started up, then died. I pulled the fuel pump relay to clear any flood. She started then died. I also noted that a relay appears to be missing and someone has jumped that circuit. I also do not see the red slash on top of the main relay (which is why I mistakenly pulled it instead of the fuel pump relay. Anyone have any ideas?

 

The main relay might be incorrect if it is missing the red slash. Google the Bosch number on the relay and see what pops up

As for the missing relay ...

What are the wire colors going into the socket? We can probably identify it from that,

Cheers
DD

 

Hi Doug,

Not sure how helpful these pictures are, but here are the wires. Looks like a black/white and a black/green. I will try to get some better pictures tomorrow.

 

Looking at similar vintage XJS diagrams, which are sometimes useful for XJ12s as well, it might be the feedback inhibit relay. If there's a problem with the feedback inhibit relay then the starter relay cannot operate...which might explain why it was bypassed.

The inhibit relay has black, white, white/black. and black/green wires.

Cheers
DD

 

Thanks, Doug, I will take a look at that and see if I can find one. Maybe borrow one from my XJS to see if it does anything. I also noted that the butterflies were not gapped properly so, I regapped those. The bushings on the butterflies are completely shot. I ordered new ones from Jonas. I need to go and rebuild the AAV. I might get that done today.

 

The relays on the V12 XJS and the V12 XJ saloon are different. Regarding the 3 relays shown in the first photo, the cylindrical red relay is the electric fan relay. The other two are the fuel pump relay in the middle and the “main” relay on the end, which indeed should have the diagonal red stripe; this relay powers the fuel pump relay and has both an 87 and an 87A connection.
There are correctly only 3 relays mounted here, none are missing from this panel. This photo is from a 1990 model V12 VDP. The main relay stripe is there, under a sticker (!).


and a 1992 V12 VDP, exactly the same layout:


and this is a 1987 V12 VDP - the same relay configuration:


and this, in contrast, is a 1990 XJS - entirely different relay plan; those yellow and blue relays on the lelft side inner fender are simply not present in the sedan system: